Biology subjects

Kogata, N.

Publications and source records attributed to Kogata, N..

6 recordsLinked to original sources

bioRxiv2026

Myofibers drive postnatal myonuclear accretion through Arp2/3-dependent membrane protrusions

Skeletal muscle postnatal growth depends on myoblast fusion with pre-existing myofibers, but whether myofibers actively regulate this process remains unclear. The Arp2/3 complex, which nucleates branched actin networks, is required for myoblast fusion during embryogenesis, but its role in postnatal myofibers is unknown. Here, we investigated the role of the Arp2/3 complex in myofibers using an inducible skeletal muscle-specific Arpc4 knockout model. We find that loss of Arp2/3 in myofibers impairs myonuclear accretion, resulting in smaller myofibers and reduced muscle strength. Satellite cells are still activated and able to differentiate but accumulate around Arpc4-deficient myofibers rather than fusing, pointing to a myofiber-intrinsic defect. In co-culture, myofibers form long-lived membrane protrusions enriched in Arp2/3 at myoblast contact sites, and optogenetic activation of protrusion in myofibers induced myoblast fusion. Genetic depletion of Arpc4 in myofibers markedly reduces membrane protrusions both in vitro and in vivo. These findings unveil a fundamental role for the Arp2/3 complex in postnatal muscle growth, and reveal a mechanism by which myofibers actively extend membrane protrusions to drive myoblast fusion. This repositions myofibers as active fusogenic partners and cell-autonomous drivers of their own nuclear accretion.

cell biology↗

bioRxiv2025

SPIN90 modulates the architecture of lamellipodial actin in an ARPC5L dependent fashion.

When stimulated by nucleation-promoting factors such as WAVE, the Arp2/3 complex generates branched actin networks. In contrast, when activated by SPIN90, the Arp2/3 complex generates linear actin filaments. The Arp2/3 complex in mammals, consists of 8 iso-complexes with dieerent properties as there are two isoforms of Arp3, ArpC1 and ArpC5. Here, using recombinant Arp2/3 iso-complexes with defined compositions, we show that SPIN90 selectively activates ArpC5L- rather than ArpC5- containing complexes to generate linear actin filaments. Consistent with this, SPIN90 at the leading edge of migrating cells enhances the recruitment of ArpC5L-, but not ArpC5- containing, Arp2/3 complexes to lamellipodia. These SPIN90-Arp2/3-ArpC5L complexes generate linear actin filaments that integrate into lamellipodia and impact protrusion eeiciency. Moreover, using polarised light microscopy, we show that loss of SPIN90 leads to an enrichment in actin filaments oriented more perpendicular to the plasma membrane. Our results demonstrate that SPIN90 regulates the architecture and dynamics of lamellipodial actin in an Arp2/3 iso-complex dependent fashion. SummarySPIN90 selectively recruits and activates ArpC5L containing Arp2/3 to shape the architecture and dynamics of lamellipodial actin.

cell biology↗

bioRxiv2024

Arp2/3 iso-complexes limit t-tubule overgrowth to ensure myofiber formation and synchronous contraction

Muscle cells form a network of plasma membrane invaginations called t-tubules that control calcium release from the endoplasmic reticulum at the triads during muscle contraction. Although the importance of t-tubules for muscle physiology is well established, and abnormalities are found in multiple disorders, the mechanisms that mediate t-tubule growth are unknown. We show that the actomyosin cortex beneath the plasma membrane, regulated by Arp2/3 complexes containing Arpc5, acts as a gatekeeper for the membrane availability required for t-tubule growth. Enlarged t-tubules are formed upon disruption of Arpc5, impairing the synchronisation between plasma membrane depolarization and calcium release. Additionally, ablation of Arpc5 postnatally in myofibers results in muscle fatigue and t-tubule abnormalities, as observed in muscle disorders. We propose that the actomyosin cortex impacts muscle function, offering a potential pathophysiological mechanism for muscle disorders.

cell biology↗

bioRxiv2024

Branched actin networks in innate immune cells mediate host microbiota homeostasis.

Assembly of branched actin networks, driven by the Arp2/3 complex are essential for the function and integrity of the immune system. Patients with loss-of-function mutations in the ARPC5 subunit of the Arp2/3 complex develop inflammation and immunodeficiency after birth, leading to early mortality. However, the mechanistic basis for these phenotypes remains obscure. Here we demonstrate that loss of Arpc5 in the murine hematopoietic system, but not the corresponding Arpc5l isoform causes early-onset intestinal inflammation after weaning. This condition is initiated by microbiota breaching the ileal mucosa, leading to local and systemic inflammation. Macrophage and neutrophils infiltrate into the ileum, but in the absence of Arpc5 fail to restrict microbial invasion. Loss of Arpc5 compromises the ability of macrophages to phagocytose and kill intra-cellular bacteria. Our results underscore the indispensable role of Arpc5, but not Arpc5l containing Arp2/3 complexes in mononuclear phagocytes function and host-microbiota homeostasis. One-Sentence SummaryArpc5 containing Arp2/3 complexes are essential for host-microbiota homeostasis

immunology↗

bioRxiv2020

MICAL2 acts through Arp3B isoform-specific Arp2/3 complexes to destabilize branched actin networks

The Arp2/3 complex (Arp2, Arp3 and ARPC1-5) is essential to generate branched actin filament networks for many cellular processes. Human Arp3, ARPC1 and ARPC5 exist as two isoforms but the functional properties of Arp2/3 iso-complexes is largely unexplored. Here we show that Arp3B, but not Arp3 is subject to regulation by the methionine monooxygenase MICAL2, which is recruited to branched actin networks by coronin-1C. Although Arp3 and Arp3B iso-complexes promote actin assembly equally efficiently in vitro, they have different cellular properties. Arp3B turns over significantly faster than Arp3 within the network and upon its depletion actin turnover decreases. Substitution of Arp3B Met293 by Thr, the corresponding residue in Arp3 increases actin network stability, and conversely, replacing Arp3 Thr293 with Gln to mimic Met oxidation promotes network disassembly. Thus, MICAL2 regulates a subset of Arp2/3 complexes to control branched actin network disassembly.

cell biology↗

bioRxiv2020

Cryo-EM of human Arp2/3 complexes provides structural insights into actin nucleation modulation by ARPC5 isoforms

The Arp2/3 complex regulates many cellular processes by stimulating formation of branched actin filament networks. Because three of its seven subunits exist as two different isoforms, mammals produce a family of Arp2/3 complexes with different properties that may be suited to different physiological contexts. To shed light on how isoform diversification affects Arp2/3 function, we determined a 4.2 [A] resolution cryo-EM structure of the most active human Arp2/3 complex containing ARPC1B and ARPC5L, and compared it with the structure of the least active ARPC1A-ARPC5-containing complex. The architecture of each isoform-specified Arp2/3 is the same. Strikingly, however, the N-terminal half of ARPC5L is partially disordered compared to ARPC5, suggesting that this region of ARPC5/ARPC5L is an important determinant of complex activity. Confirming this idea, the nucleation activity of Arp2/3 complexes containing hybrid ARPC5/ARPC5L subunits is higher when the ARPC5L N-terminus is present, thereby explaining activity differences between the different Arp2/3 complexes.

biophysics↗